The present invention relates to a software-implemented system for controlling the movement of a magnetically supported rotor and, more particularly, to such a software-implemented system for introducing selected perturbations into the movement of the rotor.
Turbomachinery, as a class, typically includes one or more rotor or rotor assemblies mounted on a bearing-supported shaft for rotation about a primary axis. In general, the rotor is subject to radially directed stress as a consequence of shaft rotation with that stress increasing with increasing rotations per unit time.
The control of unbalance forces is extremely important as rotational speeds increase. Small asymmetries in mass distribution creates rotation-dependent vibration. The fundamental frequency of the vibration, as well as the harmonics thereof, and concomitant force vectors that rapidly change magnitude and direction with each rotation can function as an operational limit on rotational speed and, with time, reduce the operating life of the components. For example, bearing life can be substantially reduced as a consequence of prolonged vibration and, in some cases, portions of the rotating mass can be subject to fatigue failures.
Various types of test beds are known for testing rotating machinery; historically, the rotor or rotor assembly is mounted in bearings and is driven at various speeds with sensors (including vibration sensors) providing a data stream for analysis.
In view of the above, it is an object of the present invention, among others, to provide a software-implemented system for controlling the rotation of a magnetically levitated rotor or rotor assembly such that various types of perturbations can be introduced into the rotor or rotor assembly.
It is an another object of the present invention, among others, to provide a software-implemented system for controlling the rotation of a magnetically levitated rotor or rotor assembly such that various types of perturbations can be introduced into the rotor or rotor assembly in order to obtain information as to the manner by which the rotor or rotor assembly responds to those input perturbations.
In accordance with the above objects, and others, the present invention advantageously provides a rotor assembly that is suspended for rotation in magnetic bearings to attain speeds higher than that for conventional bearings (i.e., ball bearings) and in which sufficient clearance is provided to allow magnetically-induced perturbations to cause abaxial rotation as well as nutation of the rotating components in response to software-driven processor commands.
The present invention provides for the creation of various types of perturbations via software control to investigate the performance of the rotor or rotor assembly under differing conditions.
In a preferred form of the invention, software or firmware controlled perturbations are introduced into the magnetic bearings that magnetically support a rotor for rotation and/or nutation about an axis. The rotational position of the rotor with time is determined and perturbations synchronously introduced into the magnetic bearing fields to create a xe2x80x9cbouncexe2x80x9d mode and/or a xe2x80x9ctiltxe2x80x9d mode. In the bounce mode, the magnetic force vectors that locate the rotor in its bearings are controlled to cause abaxial or off-axis rotation. In the tilt mode, the force vectors are controlled to cause a xe2x80x9ctiltedxe2x80x9d alignment of the rotor relative to the principal axis of the bearings; the rotor is caused to nutate about a pivot point that can be positionally adjusted.
The software/firmware of the preferred embodiment may be executed on a general or specific purpose computer and includes routines therein for effecting the desired motion. Preferably, the software/firmware includes a plurality of synthesized waveforms that can be applied to the magnetic support bearings to achieve the desired motion. For example, the waveforms can be generated by executing a recurring Fourier transform routine that create sine, sine squared, cosine, cosine squared, random, square, triangular (sawtooth) and/or other waveforms.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description to follow, taken in conjunction with the accompanying drawings, in which like parts are designated by like reference characters.